feat: keep empty cells consistent empty

CODE_GUIDELINES.md

@@ -2779,6 +2779,10 @@ Building accessible applications ensures that all users, including those with di
 
 - When `row_click` is set, the first column that does not use `col_click` gets `tabindex="0"` and `role="button"` so each row is reachable via Tab. The `TableRowKeydown` hook triggers the row action on Enter and Space (WCAG 2.1.1). Use `row_id` and `row_tooltip` for all clickable tables (e.g. Groups, Users, Roles, Members, Custom Fields, Member Fields) so the table is fully keyboard accessible.
 
+**Empty table cells (missing values):**
+
+- Do not use dashes ("-", "—", "–") or "n/a" as placeholders. Use CoreComponents `<.empty_cell sr_text="…">` for a cell with no value, or `<.maybe_value value={…} empty_sr_text="…">` when content is conditional. The cell is visually empty; screen readers get the `sr_text` (e.g. "No cycle", "No group assignment", "Not specified"). See Design Guidelines §8.6.
+
 **Tab Order:**
 
 - Ensure logical tab order matches visual order